Multicellular regulation of miR-196a-5p and miR-425-5 from adipose stem cell-derived exosomes and cardiac repair.

Cardiac transplantation of adipose-derived stem cells (ASC) modulates the post-myocardial infarction (post-MI) repair response. Biomolecules secreted or shuttled within extracellular vesicles, such as exosomes, may participate in the concerted response. We investigated the exosome's microRNAs due to their capacity to fine-tune gene expression, potentially affecting the multicellular repair response. We profiled and quantified rat ASC-exosome miRNAs and used bioinformatics to select uncharacterized miRNAs down-regulated in post-MI related to cardiac repair. We selected and validated miR-196a-5p and miR-425-5p as candidates for the concerted response in neonatal cardiomyocytes, cardiac fibroblasts, endothelial cells, and macrophages using a high-content screening platform. Both miRNAs prevented cardiomyocyte ischemia-induced mitochondrial dysfunction and reactive oxygen species production, increased angiogenesis, and polarized macrophages toward the anti-inflammatory M2 immunophenotype. Moreover, miR-196a-5p reduced and reversed myofibroblast activation and decreased collagen expression. Our data provide evidence that the exosome-derived miR-196a-5p and miR-425-5p influence biological processes critical to the concerted multicellular repair response post-MI.

Uncovering emergent phenotypes in endothelial cells by clustering of surrogates of cardiovascular risk factors.

Endothelial dysfunction (ED) is a hallmark of atherosclerosis and is influenced by well-defined risk factors, including hypoxia, dyslipidemia, inflammation, and oscillatory flow. However, the individual and combined contributions to the molecular underpinnings of ED remain elusive. We used global gene expression in human coronary artery endothelial cells to identify gene pathways and cellular processes in response to chemical hypoxia, oxidized lipids, IL-1ß induced inflammation, oscillatory flow, and these combined stimuli. We found that clustering of the surrogate risk factors differed from the sum of the individual insults that gave rise to emergent phenotypes such as cell proliferation. We validated these observations in samples of human coronary artery atherosclerotic plaques analyzed using single-cell RNA sequencing. Our findings suggest a hierarchical interaction between surrogates of CV risk factors and the advent of emergent phenotypes in response to combined stimulation in endothelial cells that may influence ED.

Oxidative phenotype induced by aerobic physical training prevents the obesity-linked insulin resistance without changes in gastrocnemius muscle ACE2-Angiotensin(1-7)-Mas axis.

BACKGROUND: We investigate the effect of aerobic physical training (APT) on muscle morphofunctional markers and Angiotensin Converting Enzyme 2/Angiotensin 1-7/Mas receptor (ACE2/Ang 1-7/Mas) axis in an obesity-linked insulin resistance (IR) animal model induced by cafeteria diet (CAF). METHODS: Male C57BL/6J mice were assigned into groups CHOW-SED (chow diet, sedentary; n = 10), CHOW-TR (chow diet, trained; n = 10), CAF-SED (n = 10) and CAF-TR (n = 10). APT consisted in running sessions of 60 min at 60% of maximal speed, 5 days per week for 8 weeks. RESULTS: Trained groups had lower body weight and adiposity compared with sedentary groups. CAF-TR improved the glucose and insulin tolerance tests compared with CAF-SED group (AUC = 28.896 ± 1589 vs. 35.200 ± 1076 mg dL-1 120 min-1; kITT = 4.1 ± 0.27 vs. 2.5 ± 0.28% min-1, respectively). CHOW-TR and CAF-TR groups increased exercise tolerance, running intensity at which VO2 max was reached, the expression of p-AMPK, p-ACC and PGC1-α proteins compared with CHOW-SED and CAF-SED. Mithocondrial protein expression of Mfn1, Mfn2 and Drp1 did not change. Lipid deposition reduced in CAF-TR compared with CAF-SED group (3.71 vs. 5.53%/area), but fiber typing, glycogen content, ACE2 activity, Ang 1-7 concentration and Mas receptor expression did not change. CONCLUSIONS: The APT prevents obesity-linked IR by modifying the skeletal muscle phenotype to one more oxidative independent of changes in the muscle ACE2/Ang 1-7/Mas axis.

Three-dimensional imaging of mitochondrial cristae complexity using cryo-soft X-ray tomography.

Mitochondria are dynamic organelles that change morphology to adapt to cellular energetic demands under both physiological and stress conditions. Cardiomyopathies and neuronal disorders are associated with structure-related dysfunction in mitochondria, but three-dimensional characterizations of the organelles are still lacking. In this study, we combined high-resolution imaging and 3D electron density information provided by cryo-soft X-ray tomography to characterize mitochondria cristae morphology isolated from murine. Using the linear attenuation coefficient, the mitochondria were identified (0.247 ± 0.04 µm-1) presenting average dimensions of 0.90 ± 0.20 µm in length and 0.63 ± 0.12 µm in width. The internal mitochondria structure was successfully identified by reaching up the limit of spatial resolution of 35 nm. The internal mitochondrial membranes invagination (cristae) complexity was calculated by the mitochondrial complexity index (MCI) providing quantitative and morphological information of mitochondria larger than 0.90 mm in length. The segmentation to visualize the cristae invaginations into the mitochondrial matrix was possible in mitochondria with MCI ≥ 7. Altogether, we demonstrated that the MCI is a valuable quantitative morphological parameter to evaluate cristae modelling and can be applied to compare healthy and disease state associated to mitochondria morphology.

NOTCH1 is critical for fibroblast-mediated induction of cardiomyocyte specialization into ventricular conduction system-like cells in vitro.

Cardiac fibroblasts are present throughout the myocardium and are enriched in the microenvironment surrounding the ventricular conduction system (VCS). Several forms of arrhythmias are linked to VCS abnormalities, but it is still unclear whether VCS malformations are cardiomyocyte autonomous or could be linked to crosstalk between different cell types. We reasoned that fibroblasts influence cardiomyocyte specialization in VCS cells. We developed 2D and 3D culture models of neonatal rat cardiac cells to assess the influence of cardiac fibroblasts on cardiomyocytes. Cardiomyocytes adjacent to cardiac fibroblasts showed a two-fold increase in expression of VCS markers (NAV1.5 and CONTACTIN 2) and calcium transient duration, displaying a Purkinje-like profile. Fibroblast-conditioned media (fCM) was sufficient to activate VCS-related genes (Irx3, Scn5a, Connexin 40) and to induce action potential prolongation, a hallmark of Purkinge phenotype. fCM-mediated response seemed to be spatially-dependent as cardiomyocyte organoids treated with fCM had increased expression of connexin 40 and NAV1.5 primarily on its outer surface. Finally, NOTCH1 activation in both cardiomyocytes and fibroblasts was required for connexin 40 up-regulation (a proxy of VCS phenotype). Altogether, we provide evidence that cardiac fibroblasts influence cardiomyocyte specialization into VCS-like cells via NOTCH1 signaling in vitro.

Aerobic exercise training prevents obesity and insulin resistance independent of the renin angiotensin system modulation in the subcutaneous white adipose tissue.

We investigate the effects of aerobic exercise training (AET) on the thermogenic response, substrate metabolism and renin angiotensin system (RAS) in the subcutaneous white adipose tissue (SC-WAT) of mice fed cafeteria diet (CAF). Male C57BL/6J mice were assigned into groups CHOW-SED (chow diet, sedentary; n = 10), CHOW-TR (chow diet, trained; n = 10), CAF-SED (CAF, sedentary; n = 10) and CAF-TR (CAF, trained; n = 10). AET consisted in running sessions of 60 min at 60% of maximal speed, five days per week for eight weeks. The CAF-SED group showed higher body weight and adiposity, glucose intolerance and insulin resistance (IR), while AET prevented such damages in CAF-TR group. AET reduced the p-AKT/t-AKT ratio and increased ATGL expression in CHOW-TR and CAF-TR groups and increased t-HSL and p-HSL/t-HSL ratio in CAF-TR. AET prevented adipocyte hypertrophy in CAF-TR group and increased UCP-1 protein expression only in CHOW-TR. Serum ACE2 increased in CHOW-TR and CAF-TR groups, and Ang (1-7) increased in the CHOW-TR group. In the SC-WAT, CAF-TR group increased the expression of AT1, AT2 and Mas receptors, whereas CHOW-TR increased Ang (1-7) and Ang (1-7)/Ang II ratio in SC-WAT. No changes were observed in ACE and Ang II. Positive correlations were observed between UCP-1 and kITT (r = 0.6), between UCP-1 and Ang (1-7) concentration (r = 0.6), and between UCP-1 and Ang (1-7)/Ang II ratio (r = 0.7). In conclusion, the AET prevented obesity and IR, reduced insulin signaling proteins and increased lipolysis signaling proteins in the SC-WAT. In addition, the CAF diet precludes the AET-induced thermogenic response and the partial modulation of the RAS suggests that the protective effect of AET against obesity and IR could not be associated with SC-WAT RAS.

Reversal of metabolic adaptations induced by physical training after two weeks of physical detraining.

The present study aimed to evaluate the effect of two weeks of physical detraining (PD) on energy balance components, white adipose tissue (WAT) metabolism, body weight (BW) and adiposity. Male C57BL/6J mice were assigned into groups sedentary (S, n = 20) and trained (T, n = 18). Physical training (PT) consisted of two 1.5 h daily sessions of swimming, 5 times/week for 4 weeks. After the PT, some of the S (S4, n = 10) and T (T4, n = 8) animals were sacrificed, and the others were kept sedentary (S6, n = 10) or detrained for two weeks (D, n = 10). After PT, the T group showed lower BW compared with S group, but PD reversed this response. The BW gains were 4%, 3% and 6.3% in S, S6 and D groups, respectively, however the T group decreased by 1.7%. T4 and D groups showed lower visceral fat depots and larger heart and left ventricle weights compared with S4 and S6 groups. Food intake, oxygen consumption at rest and fasting-induced weight loss were higher in T4 group compared with S4, and this was reversed by PD. Serum concentration of insulin, the activity of enzyme FAS and mean blood pressure did not differ among groups, but the concentration of leptin and resting heart rate were lower in T4 and D groups compared with S4 and S6 groups. T4 group increased lipolytic activity stimulated by isoproterenol and citrate synthase activity, which were reversed by PD. In conclusion, PD reversed the components of energy balance by reducing food intake and resting metabolism, and impaired WAT lipolytic activity, but not lipogenic activity. These changes resulted in remodeling of BW, but not adiposity.

Comparison between cafeteria and high-fat diets in the induction of metabolic dysfunction in mice.

This study sought to compare the metabolic responses induced by high-fat (HF) diet and cafeteria (CA) diet in mice. Adult male C57BL/6J mice were assigned into groups fed a chow (C, n=13), CA (n=12) or HF (n=11) diet during 12 weeks. Diets did not change body weight, Lee index, inguinal subcutaneous fat, the weight of organs and muscles, resting arterial pressure and heart rate. CA and HF increased visceral fat pad mass compared to C group, but only CA group showed greater adipocyte diameter and food intake compared to the C. Food intake was reduced in HF compared to C group. CA and HF showed hyperglycemia in the 3(rd), 6(th), 9(th) and 12(th) week and all values were higher in CA than HF, except in the 6(th) week. CA group showed glucose intolerance (GI) in the 6(th) week, while HF group did not show GI until the 9(th) week. CA decreased insulin sensitivity compared to C in the 12(th) week (kITT=3.3±0.2%/min vs. 4.2±0.1%/min). CA and HF groups presented higher insulin, leptin, total cholesterol, LDL-C, triglycerides and FFA levels compared to the C group. Total cholesterol and LDL-C in mg/dL were higher in the HF (161.9±7.2 and 57.5±13.4) than the CA (110.5±9.1 and 48.5±11.4), and HDL-C was higher in the HF than in the C and CA groups. In conclusion, the CA diet was more efficient to induce hyperphagia, adipocyte hypertrophy, hyperglycemia, earlier GI and insulin resistance, while the HF diet was more efficient to induce lipid profile changes.

Nutrient-adjusted high-fat diet is associated with absence of periepididymal adipose tissue inflammation: is there a link with adequate micronutrient levels?

The aim of this study was to investigate the real impact of dietary lipids on metabolic and inflammatory response in rat white adipose tissue. Male healthy Wistar rats were fed ad libitum with a control diet (CON, n=12) or with an adjusted high-fat diet (HFD, n=12) for 12 weeks. Oral glucose and insulin tolerance tests were performed during the last week of the protocol. Plasma fatty acid, lipid profile, body adiposity, and carcass chemical composition were analyzed. Plasma concentration of leptin, adiponectin, C-reactive protein (CRP), TNF-α, IL-6, and monocyte chemotactic protein (MCP-1) was measured. Periepididymal adipose tissue was employed to evaluate TNF-α, MCP-1, and adiponectin gene expression as well as NF-κB pathway and AKT proteins. Isocaloric intake of the adjusted HFD did not induce hyperphagia, but promoted an increase in periepididymal (HFD = 2.94 ± 0.77 vs. CON = 1.99 ± 0.26 g/100 g body weight, p = 0.01) and retroperitoneal adiposity (HFD = 3.11 ± 0.81 vs. CON = 2.08 ± 0.39 g/100 g body weight, p = 0.01) and total body lipid content (HFD = 105.3 ± 20.8 vs. CON = 80.5 ± 7.6 g carcass, p = 0.03). Compared with control rats, HFD rats developed glucose intolerance (p=0.01), dyslipidemia (p = 0.02) and exhibited higher C-reactive protein levels in response to the HFD (HFD = 1002 ± 168 vs. CON = 611 ± 260 ng/mL, p = 0.01). The adjusted HFD did not affect adipokine gene expression or proteins involved in inflammatory signaling, but decreased AKT phosphorylation after insulin stimulation in periepididymal adipose tissue (p = 0.01). In this study, nutrient-adjusted HFD did not induce periepididymal adipose tissue inflammation in rats, suggesting that the composition of HFD differently modulates inflammation in rats, and adequate micronutrient levels may also influence inflammatory pathways.

Dipeptidyl peptidase IV inhibition upregulates GLUT4 translocation and expression in heart and skeletal muscle of spontaneously hypertensive rats.

The purpose of the current study was to test the hypothesis that the dipeptidyl peptidase IV (DPPIV) inhibitor sitagliptin, which exerts anti-hyperglycemic and anti-hypertensive effects, upregulates GLUT4 translocation, protein levels, and/or mRNA expression in heart and skeletal muscle of spontaneously hypertensive rats (SHRs). Ten days of treatment with sitagliptin (40 mg/kg twice daily) decreased plasma DPPIV activity in both young (Y, 5-week-old) and adult (A, 20-week-old) SHRs to similar extents (~85%). However, DPPIV inhibition only lowered blood pressure in Y-SHRs (119 ± 3 vs. 136 ± 4 mmHg). GLUT4 translocation, total protein levels and mRNA expression were decreased in the heart, soleus and gastrocnemius muscle of SHRs compared to age-matched Wistar Kyoto (WKY) normotensive rats. These differences were much more pronounced between A-SHRs and A-WKY rats than between Y-SHRs and Y-WKY rats. In Y-SHRs, sitagliptin normalized GLUT4 expression in the heart, soleus and gastrocnemius. In A-SHRs, sitagliptin increased GLUT4 expression to levels that were even higher than those of A-WKY rats. Sitagliptin enhanced the circulating levels of the DPPIV substrate glucagon-like peptide-1 (GLP-1) in SHRs. In addition, stimulation of the GLP-1 receptor in cardiomyocytes isolated from SHRs increased the protein level of GLUT4 by 154 ± 13%. Collectively, these results indicate that DPPIV inhibition upregulates GLUT4 in heart and skeletal muscle of SHRs. The underlying mechanism of sitagliptin-induced upregulation of GLUT4 in SHRs may be, at least partially, attributed to GLP-1.

Leucine supplementation improves adiponectin and total cholesterol concentrations despite the lack of changes in adiposity or glucose homeostasis in rats previously exposed to a high-fat diet.

BACKGROUND: Studies suggest that leucine supplementation (LS) has a therapeutic potential to prevent obesity and to promote glucose homeostasis. Furthermore, regular physical exercise is a widely accepted strategy for body weight maintenance and also for the prevention of obesity. The aim of this study was to determine the effect of chronic LS alone or combined with endurance training (ET) as potential approaches for reversing the insulin resistance and obesity induced by a high-fat diet (HFD) in rats. METHODS: Forty-seven rats were randomly divided into two groups. Animals were fed a control diet-low fat (n = 10) or HFD (n = 37). After 15 weeks on HFD, all rats received the control diet-low fat and were randomly divided according to treatment: reference (REF), LS, ET, and LS+ET (n = 7-8 rats per group). After 6 weeks of treatment, the animals were sacrificed and body composition, fat cell volume, and serum concentrations of total cholesterol, HDL-cholesterol, triacylglycerol, glucose, adiponectin, leptin and tumor necrosis factor-alpha (TNF-α) were analyzed. RESULTS: At the end of the sixth week of treatment, there was no significant difference in body weight between the REF, LS, ET and LS+ET groups. However, ET increased lean body mass in rats (P = 0.019). In addition, ET was more effective than LS in reducing adiposity (P = 0.019), serum insulin (P = 0.022) and TNF-α (P = 0.044). Conversely, LS increased serum adiponectin (P = 0.021) levels and reduced serum total cholesterol concentration (P = 0.042). CONCLUSIONS: The results showed that LS had no beneficial effects on insulin sensitivity or adiposity in previously obese rats. On the other hand, LS was effective in increasing adiponectin levels and in reducing total cholesterol concentration.

Reversible pulmonary trunk banding. VI: Glucose-6-phosphate dehydrogenase activity in rapid ventricular hypertrophy in young goats.

OBJECTIVE: Increased myocardial glucose-6-phosphate dehydrogenase (G6PD) activity occurs in heart failure. This study compared G6PD activity in 2 protocols of right ventricle (RV) systolic overload in young goats. METHODS: Twenty-seven goats were separated into 3 groups: sham (no overload), continuous (continuous systolic overload), and intermittent (four 12-hour periods of systolic overload paired with a 12-hour resting period). During a 96-hour protocol, systolic overload was adjusted to achieve a 0.7 RV/aortic pressure ratio. Echocardiographic and hemodynamic evaluations were performed before and after systolic overload every day postoperatively. After the study period, the animals were humanely killed for morphologic and G6PD tissue activity assessment. RESULTS: A 92.1% and 46.5% increase occurred in RV and septal mass, respectively, in the intermittent group compared with the sham group; continuous systolic overload resulted in a 37.2% increase in septal mass. A worsening RV myocardial performance index occurred in the continuous group at 72 hours and 96 hours, compared with the sham (P < .039) and intermittent groups at the end of the protocol (P < .001). Compared with the sham group, RV G6PD activity was elevated 130.1% in the continuous group (P = .012) and 39.8% in the intermittent group (P = .764). CONCLUSIONS: Continuous systolic overload for ventricle retraining causes RV dysfunction and upregulation of myocardial G6PD activity, which can elevate levels of free radicals by NADPH oxidase, an important mechanism in the pathophysiology of heart failure. Intermittent systolic overload promotes a more efficient RV hypertrophy, with better preservation of myocardial performance and and less exposure to hypertrophic triggers.

The role of inflamed adipose tissue in the insulin resistance.

In this article, we discuss inflammation associated with adipose tissue dysfunction as a potential link with obesity-related insulin resistance, and how obesity-related inflammatory components, such as immune cells, cytokines/chemokines and adipocytokines, induce obesity-related pathologies.

High sodium intake enhances insulin-stimulated glucose uptake in rat epididymal adipose tissue.

OBJECTIVE: This study investigated the effect of different sodium content diets on rat adipose tissue carbohydrate metabolism and insulin sensitivity. METHODS AND PROCEDURES: Male Wistar rats were fed on normal- (0.5% Na(+); NS), high- (3.12% Na(+); HS),or low-sodium (0.06% Na(+); LS) diets for 3, 6, and 9 weeks after weaning. Blood pressure (BP) was measured using a computerized tail-cuff system. An intravenous insulin tolerance test (ivITT) was performed in fasted animals. At the end of each period, rats were killed and blood samples were collected for glucose and insulin determinations. The white adipose tissue (WAT) from abdominal and inguinal subcutaneous (SC) and periepididymal (PE) depots were weighed and processed for adipocyte isolation and measurement of in vitro rates of insulin-stimulated 2-deoxy-D-[(3)H]-glucose uptake (2DGU) and conversion of -[U-(14)C]-glucose into (14)CO(2). RESULTS: After 6 weeks, HS diet significantly increased the BP, SC and PE WAT masses, PE adipocyte size, and plasma insulin concentration. The sodium dietary content did not influence the whole-body insulin sensitivity. A higher half-maximal effective insulin concentration (EC(50)) from the dose-response curve of 2DGU and an increase in the insulin-stimulated glucose oxidation rate were observed in the isolated PE adipocytes from HS rats. DISCUSSION: The chronic salt overload enhanced the adipocyte insulin sensitivity for glucose uptake and the insulin-induced glucose metabolization, contributing to promote adipocyte hypertrophy and increase the mass of several adipose depots, particularly the PE fat pad.

High dietary sodium intake increases white adipose tissue mass and plasma leptin in rats.

OBJECTIVE: Salt restriction has been reported to increase white adipose tissue (WAT) mass in rodents. The objective of this study was to investigate the effect of different sodium content diets on the lipogenic and lipolytic activities of WAT. RESEARCH METHODS AND PROCEDURES: Male Wistar rats were fed on normal-sodium (NS; 0.5% Na(+)), high-sodium (HS; 3.12% Na(+)), or low-sodium (LS; 0.06% Na(+)) diets for 3, 6, and 9 weeks after weaning. Blood pressure (BP) was measured using a computerized tail-cuff system. At the end of each period, rats were killed and blood samples were collected for leptin determinations. The WAT from abdominal and inguinal subcutaneous (SC), periepididymal (PE) and retroperitoneal (RP) depots was weighed and processed for adipocyte isolation, rate measurement of lipolysis and d-[U-(14)C]-glucose incorporation into lipids, glucose-6-phosphate dehydrogenase (G6PDH) and malic enzyme activity evaluation, and determination of G6PDH and leptin mRNA expression. RESULTS: After 6 weeks, HS diet significantly increased BP; SC, PE, and RP WAT masses; PE adipocyte size; plasma leptin concentration; G6PDH activity in SC WAT; and PE depots and malic activity only in SC WAT. The leptin levels correlated positively with WAT masses and adipocyte size. An increase in the basal and isoproterenol-stimulated lipolysis and in the ability to incorporate glucose into lipids was observed in isolated adipocytes from HS rats. DISCUSSION: HS diet induced higher adiposity characterized by high plasma leptin concentration and adipocyte hypertrophy, probably due to an increased lipogenic capacity of WAT.

Pinealectomy reduces hepatic and muscular glycogen content and attenuates aerobic power adaptability in trained rats.

The current study emphasizes the crucial role of the pineal gland on the effects of chronic training in different tissues focusing on carbohydrate metabolism. We investigated the maximal oxygen uptake (aerobic power), muscle and liver glycogen content, and also the enzymes involved in the carbohydrate metabolism of rat adipose tissue. Pinealectomized and sham-operated adult male Wistar rats were distributed into four groups: pinealectomized (PINX) untrained, pinealectomized trained, control untrained and control trained. The maximal oxygen uptake capability was assayed before and after the training protocol by indirect open circuit calorimetry. The rats were killed after 8 wk of training. Blood samples were collected for glucose and insulin determinations. The glycogen content was assayed in the liver and muscle. Maximal activities of epididymal adipose tissue enzymes (hexokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase and malic enzyme) as well as adipocyte size were determined. The exercise training in control animals promoted an increase in the aerobic power and in liver glycogen content but caused a reduction in the malic enzyme activity in adipose tissue. However, PINX trained animals, in contrast to trained controls, showed a decrease in the aerobic power and in liver and muscle glycogen content, as well as an increase in the activity of the adipocyte enzymes involved in carbohydrate metabolism. In conclusion, these data show that the pineal gland integrity is necessary for the homeostatic control of energy metabolism among adipose, muscle and hepatic tissues. The pinealectomized animals showed alterations in adaptive responses of the maximal oxygen uptake to training. Therefore, the pineal gland must be considered an influential participant in the complex adaptation to exercise and is involved in the improvement of endurance capacity.

Neonatal streptozotocin-induced diabetes mellitus: a model of insulin resistance associated with loss of adipose mass.

The use of experimental models of diabetes mellitus (DM) has been useful in understanding the complex pathogenesis of DM. Streptozotocin (STZ) injected in rats during the neonatal period has usually led to the major features described in diabetic patients (hyperglycemia, polyphagia, polydipsia, polyuria, and abnormal glucose tolerance) in a short period. Diabetes mellitus is a product of low insulin sensibility and pancreatic beta-cell dysfunction. Its process is characterized by a symptomless prediabetic phase before the development of the disease. In this study, we investigated the long-term effects of diabetes induction regarding the cellular metabolic aspects of this model and its similarities with diabetes found in humans. Male Wistar rats (5-day old) were intraperitoneally injected with STZ (150 mg/kg) and followed up for 12 weeks. On the 12th week, animals were decapitated and peri-epididymal fat pads were excised for adipocyte isolation. The following studies were performed: insulin-stimulated 2-deoxy-d-[(3)H]glucose uptake; incorporation of d-[U-(14)C]-glucose into lipids and conversion into (14)CO(2); and insulin binding. The weight gain rate of the STZ-treated group became significantly lower by the eighth week. These rats developed polyphagia, polydipsia, polyuria, and glycosuria, and impaired glucose tolerance. Biological tests with isolated adipocytes revealed a reduction in the insulin receptor number and an impairment in their ability to oxidize glucose as well as to incorporate it into lipids. Interestingly, parallel to reduced body weight, the adipocyte size of STZ rats was significantly small. We concluded that apart of a decrease in pancreatic insulin content, this experimental model of DM promotes a remarkable and sustained picture of insulin resistance in adulthood that is strongly related to a loss in adipose mass.

[The adipose tissue as a regulatory center of the metabolism]. / O tecido adiposo como centro regulador do metabolismo.

The recent progress in the research about the metabolic properties of the adipose tissue and the discovery of its ability to produce hormones that are very active in pathophysiologic as well as physiologic processes is rebuilding the concepts about its biology. Its involvement in conditions like obesity, type 2 diabetes mellitus, arterial hypertension, arteriosclerosis, dislipidemias and chronic and acute inflammatory processes indicate that the understanding of its functional capacities may contribute to improve the prognosis of those diseases whose prevalence increased in a preoccupying manner. Here we review some functional aspects of adipocytes, such as the metabolism, its influence on energy homeostasis, its endocrine ability and the adipogenesis, i.e., the potential of pre-adipocytes present in adipose tissue stroma to differentiate into new adipocytes and regenerate the tissue. In addition, we are including some studies on the relationship between the adipose tissue and the pineal gland, a new and poorly known, although, as will be seen, very promising aspect of adipocyte physiology together with its possible favorable repercussions to the therapy of the obesity related diseases.

O tecido adiposo como centro regulador do metabolismo / The adipose tissue as a regulatory center of the metabolism

Os avanços da pesquisa sobre as propriedades metabólicas do tecido adiposo e as recentes descobertas sobre sua capacidade em produzir hormônios atuantes em processos fisiológicos e fisiopatológicos, estão revolucionando conceitos sobre a sua biologia. O seu envolvimento em processos como obesidade, diabetes mellitus tipo 2, hipertensão arterial, arteriosclerose, dislipidemias, processos inflamatórios agudos e crônicos, entre outros, indicam que a compreensão das suas propriedades funcionais contribuirão para melhorar o prognóstico daquelas doenças, cuja prevalência vem crescendo de forma preocupante. Nesta revisão, abordamos aspectos funcionais dos adipócitos, como o metabolismo, a participação na homeostase energética, a sua habilidade endócrina e a adipogênese, entendida como a capacidade de pré-adipócitos, presentes no parênquima do tecido, de se diferenciarem em novos adipócitos e reconstituírem o tecido. Além disso, estamos incluindo estudos sobre as relações entre o tecido adiposo e a glândula pineal, aspecto novo e pouco conhecido, mas, como será visto, muito promissor da fisiologia do adipócito com possíveis repercussões favoráveis para a terapêutica das moléstias relacionadas com a obesidade.

The recent progress in the research about the metabolic properties of the adipose tissue and the discovery of its ability to produce hormones that are very active in pathophysiologic as well as physiologic processes is rebuilding the concepts about its biology. Its involvement in conditions like obesity, type 2 diabetes mellitus, arterial hypertension, arteriosclerosis, dislipidemias and chronic and acute inflammatory processes indicate that the understanding of its functional capacities may contribute to improve the prognosis of those diseases whose prevalence increased in a preoccupying manner. Here we review some functional aspects of adipocytes, such as the metabolism, its influence on energy homeostasis, its endocrine ability and the adipogenesis, i.e., the potential of pre-adipocytes present in adipose tissue stroma to differentiate into new adipocytes and regenerate the tissue. In addition, we are including some studies on the relationship between the adipose tissue and the pineal gland, a new and poorly known, although, as will be seen, very promising aspect of adipocyte physiology together with its possible favorable repercussions to the therapy of the obesity related diseases.

Reduced lipolysis and increased lipogenesis in adipose tissue from pinealectomized rats adapted to training.

The current study investigated the effects of chronic training and pinealectomy on the lipogenic and lipolytic activity of adipose tissue. Pinealectomized and sham-operated adult male Wistar rats were distributed in to four subgroups: pinealectomized untrained, pinealectomized trained, control untrained and control trained. At the end of the training period (8 wk) the rats were killed. Blood samples were collected for glucose, insulin and leptin determinations. Peri-epididymal adipocytes were isolated for measurement of in vitro rates of lipolysis and incorporation of substrates (D-[U-14C]-glucose, L-[U-14C]-lactate, [2-14C]-acetate and [1-14C]-palmitate) into lipids, and samples of epididymal adipose tissue were homogenized for evaluation of glucose-6-phosphate dehydrogenase maximal activity. Pinealectomy resulted in a significantly increased lipolytic capacity in response to isoproterenol and a decrease in circulating leptin levels without affecting the rates of incorporation of different substrates into lipids. However, only in the intact control group did training promote a higher basal and isoproterenol-stimulated lipolysis, increase the incorporation of palmitate (esterification), decrease the incorporation of acetate (lipogenesis) into lipids and diminish circulating leptin levels. These effects of exercise training were not seen in pinealectomized rats. However, pinealectomized trained animals showed a marked reduction in lipolysis and an increased rate of acetate incorporation. In conclusion, we demonstrated for the first time that the pineal gland plays an important role in the regulation of lipid metabolism in such a way that its absence caused a severe alteration in the balance between lipogenesis and lipolysis, which becomes evident with the adaptation to exercise training.